1. Field of the Invention
This invention relates generally to the field of plating or etching of three dimensional molded parts such as printed wiring boards or electrical connectors. More particularly, this invention relates to a method which can be used to plate or etch conductive patterns onto molded plastic parts to produce three dimensional circuit boards, electrical connectors and the like using a resilient laser etched mask.
2. Background of the Invention
While it has been possible to produce three dimensional plated or etched parts in the past, masks used in these plating and etching processes have always been rigid and usually made from machined metals. Typically, such masks were made of machined aluminum with the plating patterns machined into the surface of the mask. Such machined masks suffer from a number of problems including relatively poor line resolution limited by the precision with which the mask could be machined. This results in lines which are typically limited to about 0.020 inch line widths and 0.030 inch line spacings. In order to obtain higher circuit densities which are used for printed wiring board (PWB) applications, much narrower width and closer spacing is required.
It is also not possible to make certain patterns using machined masks. This is due to the inability of a machined mask to support isolated areas of mask material. That is, mechanical support must be provided for all portions of the mask.
Such machined masks are generally negative image masks in which material is only present in locations where metal patterns are to be removed (or not deposited) on the part. It is thus not usually possible to manufacture a positive image mask. This limits the manufacturing process to those using a negative image mask.
In addition, it is extremely difficult to manufacture a machined rigid mask which intimately contacts the surface of the part being plated under all reasonable extremes of manufacturing tolerance. This can further influence the sharpness of the lines and impair resolution and line density.
Other processes for producing molded plastic circuit board are disclosed in U.S. Pat. Nos. 4,584,767 and 4,710,419 both to Gregory and in U.S. Pat. No. 4,591,220 to Impey. None of these patents utilize the method or apparatus disclosed herein.
The above-described shortcomings with the prior art processes are ameliorated with the present process in which a flexible mask having opaque and clear areas are brought into intimate contact with the part being plated using a vacuum.